1. Field of the Invention
The present invention relates to processing identifiers, also called addresses, of user installation telephone terminals for telephone calls via a packet transmission network. To be more precise, the invention relates to transmitting voice over a high bit rate packet transmission network such as the internet network.
2. Description of the Prior Art
In telephone systems based on packet transmission networks, such as the internet network, it is necessary to identify in a biunivocal manner the various terminals served by the network so that they can send and receive telephone call packets. A single identifier, such as an Internet Protocol (IP) address, is associated with each terminal worldwide. If it is included as a destination address in a packet, the IP address is used to route the packet through the network.
The IPv4 address conforming to version 4 of the Internet Protocol contains 32 bits, i.e. 4 bytes, which represents only around four billion potential terminal identifiers. Because many addresses are already used by microcomputers to connect to the internet network, using the IPv4 address as a terminal identifier limits addressing capacity in the internet network. Consequently, this limited addressing capacity restricts expansion of access to the internet network to all telephone terminals to which telephone services based on packet transmission networks such as the internet should be available.
To remedy the shortfall of internet addressing capacity, a new protocol according to a version 6 is intended to expand IPv6 terminal addresses to 128 bits. The 128 bits of the IPv6 address can define a very large number of terminal identifiers, in fact approximately 3×1038 potential identifiers. Although it is intended to encapsulate IPv4 addresses in IPv6 addresses to facilitate the transition between version 4 and version 6 of the internet protocol, there is at present no telephone terminal on the internet network designated by an IPv6 address.
It will be noticed that the invention does not relate to an address conversion between networks using the IPv4 protocol and the IPv6 protocol, as described in the patent application EP 0 840 482.
In telecommunication networks based on circuit switching, terminals connected directly to an access network are identified by the number of their access, such as a telecommunication line. When terminals are connected to an access network via a client installation, each terminal has a private identifier used only locally within the installation, and only the client installation is designated by a unique number enabling the installation to access the access network.
If the terminals of a client installation must be identifiable individually from outside the installation, it is necessary to allocate each of the terminals of the installation one identifier. For example, if a client digital telephone installation is connected to an integrated service digital network, the network operator can respectively allocate telephone numbers to the terminals of the client installation, which then becomes transparent in terms of addressing the terminals.
In telecommunication networks based on packet switching, for example the internet network, each terminal must be identified bijectively and therefore unambiguously in order for it to be able to dialog with other terminals or application servers via the packet transmission network. Each terminal must therefore have its own identifier to distinguish it from other terminals. The identifier of the terminal is uniquely defined worldwide to ensure consistency with the existing network.
For telephone services based on packet transmission networks, i.e. networks routing voice by means of packets, this bijective identification is particularly important. Because it must be possible to call a terminal at any time, its identifier must be known and validated by the packet network.
There are also client telecommunication installations in which terminals are connected by an intranet network based on the internet protocol and consequently have IP format private addresses respectively allocated to the terminal internally. To prevent addressing ambiguities, for example if the client installation must be connected to the internet network, a translator device is included at the installation access level for translating each IP private terminal address into a public terminal address so that each terminal of the installation can be addressed from outside the installation.